Create new "Add track workflow" that allows pasting JSON track configs

[cmdcolin]

This is a very simple component that let's users paste a config in plain JSON format

This would be an escape hatch for expert users or perhaps users getting instruction. sometimes I imagine it being helpful in a workshop for users to paste a particular thing rather than click and edit the GUI a bunch after adding the basic instance of a track

sort of the GUI version of the add-track-json CLI

[codecov]

Codecov Report

Merging #3277 (a539610) into main (b903476) will decrease coverage by 0.02%.
The diff coverage is 5.88%.

❗ Current head a539610 differs from pull request most recent head 4c65301. Consider uploading reports for the commit 4c65301 to get more accurate results

@@            Coverage Diff             @@
##             main    #3277      +/-   ##
==========================================
- Coverage   59.19%   59.16%   -0.03%     
==========================================
  Files         749      750       +1     
  Lines       29240    29257      +17     
  Branches     7083     7084       +1     
==========================================
+ Hits        17308    17310       +2     
- Misses      11683    11698      +15     
  Partials      249      249              

Impacted Files	Coverage Δ
...t/src/AddTrackWidget/components/AddTrackWidget.tsx	90.90% <ø> (ø)
...lugins/data-management/src/AddTrackWidget/model.ts	83.72% <ø> (ø)
.../AddTrackWidget/components/PasteConfigWorkflow.tsx	5.88% <5.88%> (ø)
products/jbrowse-web/src/util.ts	48.33% <0.00%> (ø)
...rative-view/src/ServerSideRenderedBlockContent.tsx	66.66% <0.00%> (+4.16%)	⬆️

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[cmdcolin]

now that we have these workflows, moving forward with a multi-track adder may be valuable...paste list of URLs, etc.